Adaptive voltage control for wind turbines

Abstract

Systems and methods are provided herein for configuring and/or operating a wind turbine to adaptively control a voltage of a power grid. In one or more embodiments, a method and system for recognizing a condition of a power grid (e.g., fluctuations caused by variable consumer loads on a weak grid), and adaptively adjusting a voltage control scheme to “ignore” voltage changes caused by the condition are provided. Additionally, other features of the present invention includes a voltage control with active power derating for wind turbines and power factor control with active power derating for wind turbines. The active power derating features of the present invention may be dependent upon physical characteristics of a synchronous generator associated with the wind turbine.

1 . A method of operation for a wind turbine connected to a power grid, wherein the wind turbine comprises a synchronous generator, the method comprising the steps of:
 maintaining an electrically-connected status between the wind turbine and the power grid; and   operating the wind turbine to selectively control a reactive power characteristic of the synchronous generator according to a control scheme during the maintaining step, wherein the operating step comprises:   recognizing a predefined condition of the power grid; and   in response to the recognizing step, modifying the control scheme to reduce the amount of reactive power absorbed by the synchronous generator.   
     
     
         2 . (canceled) 
     
     
         3 . (canceled) 
     
     
         4 . The method of  claim 1 , wherein the recognizing step comprises:
 measuring a reactive power characteristic of the synchronous generator for a period of time during the maintaining step.   
     
     
         5 . The method of  claim 1 , wherein the recognizing step comprises:
 analyzing a reactive power characteristic of the synchronous generator for a period of time during the maintaining step.   
     
     
         6 . (canceled) 
     
     
         7 . (canceled) 
     
     
         8 . The method of any of  claim 1 , wherein the modifying step comprises:
 generating an adapted control reference; and   providing the adapted control reference to the control scheme.   
     
     
         9 . The method of  claim 8 , wherein the generating an adapted control reference step comprises:
 generating a first voltage reference dependent upon a measured reactive power characteristic of the synchronous generator; and   adding a nominal voltage reference to the first voltage reference to generate the adapted control reference.   
     
     
         10 . The method of  claim 8 , wherein the adapted control reference is an adapted voltage reference, the operating step further comprising:
 receiving the adapted voltage reference during the maintaining step;   measuring a voltage of the power grid during the maintaining step; and   selectively controlling a reactive power characteristic of the synchronous generator such that the measured voltage of the power grid substantially tracks the adapted voltage reference.   
     
     
         11 . The method of  claim 8 , wherein the adapted control reference is limited to a range that is dependent upon a rated voltage of the power grid. 
     
     
         12 . The method of  claim 11 , wherein the range is 95 percent to 105 percent of the rated voltage of the power grid. 
     
     
         13 . The method of  claim 1 , wherein the modifying step comprises:
 adjusting a rotor current of the synchronous generator to reduce the amount of reactive power absorbed by the synchronous generator.   
     
     
         14 . The method of  claim 1 , wherein the control scheme is implemented utilizing an automatic voltage regulator (AVR), the AVR being operative to receive a voltage reference, measure a voltage of the power grid, and control the voltage of the power grid to track the voltage reference by selectively adjusting a rotor current of the synchronous generator, and wherein the modifying step comprises:
 adapting the voltage reference dependent upon the recognizing step.   
     
     
         15 . A method of operation for a wind turbine connected to a power grid, wherein the wind turbine comprises a synchronous generator, the method comprising the steps of:
 maintaining an electrically-connected status between the wind turbine and the power grid;   executing a first operating step comprising operating the wind turbine in a first active power control mode for a first condition during the maintaining step; and   executing a second operating step comprising operating the wind turbine in a second active power control mode for a second condition during the maintaining step, wherein the second operating step provides a different active power characteristic for the wind turbine than the first operating step.   
     
     
         16 . (canceled) 
     
     
         17 . The method of  claim 15 , wherein the first condition and the second condition are each dependent upon a voltage of the power grid. 
     
     
         18 . (canceled) 
     
     
         19 . The method of  claim 15 , wherein the first condition and second condition are each determined by performing the steps of:
 measuring a voltage of the power grid during the maintaining step;   analyzing the measured voltage of the power grid; and   operating the wind turbine in either the first active power control mode or the second active power control mode dependent upon the analyzing step.   
     
     
         20 . The method of  claim 19 , wherein the analyzing step comprises:
 comparing the measured voltage with a threshold voltage reference over a period of time.   
     
     
         21 . The method of  claim 20 , wherein the comparing step comprises:
 integrating a difference of the measured voltage and the threshold voltage reference.   
     
     
         22 . The method of  claim 21 , further comprising:
 operating the wind turbine in one of the first active power control mode and the second active power control mode dependent upon the integrating step.   
     
     
         23 . The method of  claim 15 , wherein the active power characteristic is reduced when operating in the second active power control mode relative to the first active power control mode by an amount that is dependent upon a measured voltage of the power grid. 
     
     
         24 . The method of  claim 15 , wherein the active power characteristic is reduced when operating in the second active power control mode relative to the first active power control mode by an amount that is proportional to an integral of the difference between a measured voltage of the power grid and a maximum voltage reference. 
     
     
         25 . The method of  claim 15 , wherein the first condition and the second condition are each dependent upon a power factor reference. 
     
     
         26 . The method of  claim 25 , wherein the first condition and second condition are determined by performing the steps of:
 receiving a power factor reference;   comparing the power factor reference to a power factor capability of the synchronous generator; and   operating the wind turbine in either the first active power control mode or the second active power control mode dependent upon the comparing step.   
     
     
         27 . The method of  claim 25 , wherein the active power characteristic is reduced when operating in the second active power control mode relative to the first active power control mode by an amount that is dependent upon one or more physical characteristics of the synchronous generator. 
     
     
         28 - 33 . (canceled) 
     
     
         34 . The method of  claim 15 , wherein the wind turbine comprises a turbine rotor coupled to the synchronous generator with a torque regulator, wherein the first operating step or the second operating step comprises:
 adjusting operation of the torque regulator.   
     
     
         35 . The method of  claim 34 , wherein the adjusting operation of the torque regulator step comprises adjusting an amount of torque that is transferred from the turbine rotor to the synchronous generator. 
     
     
         36 . The method of  claim 15 , wherein the wind turbine comprises a turbine rotor coupled to the synchronous generator through a torque-regulating gearbox (TRG), wherein the first operating step or the second operating step comprises:
 adjusting operation of the TRG.   
     
     
         37 . The method of  claim 36 , wherein the adjusting operation step comprises adjusting a torque conversion characteristic of the TRG. 
     
     
         38 . The method of  claim 36 , wherein the TRG comprises a hydraulic circuit, and wherein the adjusting operation step comprises:
 adjusting a mass flow of hydraulic fluid through the hydraulic circuit.   
     
     
         39 . The method of  claim 36 , wherein the TRG comprises a plurality of guide vanes disposed in a guide vanes housing, and wherein the adjusting operation step comprises:
 adjusting a position of the plurality of guide vanes.   
     
     
         40 . The method of  claim 36 , wherein the adjusting operation step comprises:
 adjusting an amount of energy absorbed by the TRG.   
     
     
         41 . A method for adaptively controlling a voltage for a generator of wind turbine connected to a power grid, the method comprising:
 measuring a reactive power characteristic of the generator over a period of time;   processing the reactive power characteristic measurements to generate a corrected voltage factor;   adding the corrected voltage factor to a nominal voltage reference to generate an adapted voltage reference; and   providing the adapted voltage reference to an automatic voltage regulator (AVR) of the wind turbine.   
     
     
         42 . The method of  claim 41 , wherein the processing comprises applying a PI controller to the reactive power measurements. 
     
     
         43 . The method of  claim 42 , wherein the PI controller comprises a time constant that is greater than an hour. 
     
     
         44 . The method of  claim 41 , wherein the wind turbine comprises a synchronous generator, and wherein the AVR is operable to adjust the reactive power characteristic by adjusting a rotor current of the synchronous generator. 
     
     
         45 . The method of  claim 41 , wherein the adapted local voltage reference range is between about 95% and 105% of a rated voltage of the power grid. 
     
     
         46 . The method of any of  claims 41 - 45 , further comprising:
 limiting the corrected voltage factor to within a predefined range.   
     
     
         47 . The method of  claim 41 , further comprising applying a low pass filter to the measured reactive power characteristic. 
     
     
         48 . The method of  claim 41 , further comprising subtracting a nominal reactive power reference from the measured reactive power characteristic. 
     
     
         49 - 76 . (canceled) 
     
     
         77 . A method for controlling the active power delivery for a generator of a wind turbine connected to a power grid, the method comprising:
 receiving a threshold voltage reference;   measuring a voltage of the power grid;   subtracting the measured voltage from the threshold voltage reference to generate a voltage difference value;   processing the voltage difference value to generate a voltage mode adapted active power reference;   receiving a power factor reference;   analyzing the power factor reference in relation to one or more physical capabilities of the generator;   generating an power factor mode adapted active power reference that is dependent upon the power factor reference and the one or more physical capabilities of the generator;   determining the minimum between the power factor mode adapted active power reference and the voltage mode adapted active power reference to generate a minimum adapted active power reference; and   providing the minimum adapted active power reference to an active power controller of the wind turbine generator.   
     
     
         78 . The method of  claim 77 , further comprising:
 limiting each of the power factor mode adapted active power reference and the voltage mode adapted active power reference to within a predetermined range.   
     
     
         79 . The method of  claim 77 , wherein the processing comprises:
 applying an integrator to the voltage difference value.   
     
     
         80 . The The method of  claim 77 , wherein the threshold voltage reference is between about 101% and 105% of a rated voltage of the power grid. 
     
     
         81 . The method of any  claim 77 , the threshold voltage reference is dependent upon a maximum reactive power that can be consumed by the synchronous generator when operating at a rated active power. 
     
     
         82 . The method of  claim 77 , wherein the active power delivery is reduced by an amount that is dependent upon at least one of the processing step and the analyzing step. 
     
     
         83 . The method of  claim 77 , wherein the generator is a synchronous generator. 
     
     
         84 . The method of  claim 77 , wherein the analyzing step comprises:
 comparing the power factor reference with the one or more physical capabilities of the generator.   
     
     
         85 . The method of  claim 77 , further comprising:
 limiting the power factor reference to be within a predefined range.   
     
     
         86 . The method of  claim 77 , further comprising:
 reducing an active power delivery of the generator.   
     
     
         87 . The method of  claim 86 , wherein the wind turbine comprises a turbine rotor coupled to the synchronous generator with a torque regulator, wherein the first operating step or the second operating step comprises:
 adjusting operation of the torque regulator.   
     
     
         88 . The method of  claim 87 , wherein the adjusting operation of the torque regulator step comprises adjusting an amount of torque that is transferred from the turbine rotor to the synchronous generator. 
     
     
         89 . The method of  claim 86 , wherein the generator is a synchronous generator, and wherein the wind turbine comprises a turbine rotor coupled to the synchronous generator through a torque-regulating gearbox (TRG), the reducing step comprising:
 adjusting operation of the TRG.   
     
     
         90 . The method of  claim 89 , wherein the adjusting operation step comprises adjusting a torque conversion characteristic of the TRG. 
     
     
         91 . The method of  claim 89 , wherein the TRG comprises a hydraulic circuit, and wherein the adjusting operation step comprises:
 adjusting a mass flow of hydraulic fluid through the hydraulic circuit.   
     
     
         92 . The method of  claim 89 , wherein the TRG comprises a plurality of guide vanes disposed in a guide vanes housing, and wherein the adjusting operation step comprises:
 adjusting a position of the plurality of guide vanes.   
     
     
         93 . The method of  claim 89 , wherein the adjusting operation step comprises:
 adjusting an amount of energy absorbed by the TRG.   
     
     
         94 - 107 . (canceled) 
     
     
         108 . A wind turbine connected to a power grid, the wind turbine comprising:
 a synchronous generator electrically connected to the power grid; and   control logic comprising a first active power control mode for operating the wind turbine during a first condition, and further comprising a second active power control mode for operating the wind turbine during a second condition, wherein operating the wind turbine in the second active power control mode provides a different active power characteristic for the wind turbine than when operating the wind turbine in the first active power control mode.   
     
     
         109 . (canceled) 
     
     
         110 . The wind turbine of  claim 108 , wherein the first condition and the second condition are each dependent upon a voltage of the power grid. 
     
     
         111 . (canceled) 
     
     
         112 . The wind turbine of  claim 108 , wherein the control logic is configured to identify an occurrence of each of the first condition and second condition by measuring a voltage of the power grid and analyzing the measured voltage of the power grid. 
     
     
         113 . The wind turbine of  claim 112 , wherein the control logic is configured to identify an occurrence of each of the first condition and second condition by comparing the measured voltage with a threshold voltage reference over a period of time. 
     
     
         114 . The wind turbine of  claim 113 , wherein the control logic is configured to identify an occurrence of each of the first condition and second condition by integrating a difference of the measured voltage and the threshold voltage reference. 
     
     
         115 . The wind turbine of  claim 114 , wherein the control logic is configured to operate the wind turbine in one of the first active power control mode and the second active power control mode dependent upon the integrating the difference of the measured voltage and the threshold voltage reference. 
     
     
         116 . The wind turbine of  claim 108 , wherein the control logic is configured to reduce the active power characteristic when operating the wind turbine in the second active power control mode relative to the first active power control mode by an amount that is dependent upon a measured voltage of the power grid. 
     
     
         117 . The wind turbine of  claim 108 , wherein the control logic is configured to reduce the active power characteristic when operating the wind turbine in the second active power control mode relative to the first active power control mode by an amount that is proportional to an integral of the difference between a measured voltage of the power grid and a maximum voltage reference. 
     
     
         118 . The wind turbine of  claim 108 , wherein the first condition and the second condition are each dependent upon a power factor reference. 
     
     
         119 . The wind turbine of  claim 118 , wherein the control logic is configured to identify an occurrence of each of the first condition and second condition by receiving a power factor reference, and comparing the power factor reference to a power factor capability of the synchronous generator. 
     
     
         120 . The wind turbine of  claim 118 , wherein the control logic is configured to reduce the active power characteristic when operating the wind turbine in the second active power control mode relative to the first active power control mode by an amount that is dependent upon one or more physical characteristics of the synchronous generator. 
     
     
         121 - 126 . (canceled) 
     
     
         127 . The wind turbine of  claim 108 , wherein the wind turbine comprises a turbine rotor coupled to the synchronous generator with a torque regulator, wherein the control logic is configured to adjust operation of the torque regulator. 
     
     
         128 . The wind turbine of  claim 127 , wherein the control logic is configured to adjust an amount of torque that is transferred from the turbine rotor to the synchronous generator. 
     
     
         129 . The wind turbine of  claim 108 , wherein the wind turbine comprises a turbine rotor coupled to the synchronous generator through a torque-regulating gearbox (TRG), wherein the control logic is configured to adjust operation of the TRG. 
     
     
         130 . The wind turbine of  claim 129 , wherein the control logic is configured to adjust a torque conversion characteristic of the TRG. 
     
     
         131 . The wind turbine of  claim 129 , wherein the TRG comprises a hydraulic circuit, and wherein the control logic is configured to adjust a mass flow of hydraulic fluid through the hydraulic circuit. 
     
     
         132 . The wind turbine of  claim 129 , wherein the TRG comprises a plurality of guide vanes disposed in a guide vanes housing, and wherein the control logic is configured to adjust a position of the plurality of guide vanes. 
     
     
         133 . The wind turbine of  claim 129 , wherein the control logic is configured to adjust an amount of energy absorbed by the TRG 
     
     
         134 . A wind turbine connected to a power grid, the wind turbine comprising:
 a synchronous generator electrically connected to the power grid; and   control logic that is configured to:   receive a reactive power characteristic of the generator over a period of time;   process the reactive power characteristic measurement to generate a corrected voltage factor;   add the corrected voltage factor to a nominal voltage reference to generate an adapted voltage reference; and   provide the adapted voltage reference to an automatic voltage regulator (AVR) of the wind turbine.   
     
     
         135 - 139 . (canceled)